New to Lemmy

For those on smaller instances/sites, you may have to use Lemmyverse to find communities first due to how things work here.

As to how to check whether you're on a larger instance/site...Lemmyverse helps again, just switched to instance view. If you're along the top of the grid (or list), you're in a larger instance.

For those on larger instances/sites, chances are you're already connected to a variety of existing communities. Given that, it's better to search first, making sure search isn't set to Local but instead All, before jumping into creating one. If you want to be more thorough, use the above Lemmyverse link to double check that there's not another active community already out there.

All that said, if you do find another community and it's active, yet seems not to match the approach you'd like to take, then go for making a new community. However consider giving it a distinct name and/or sidebar info to make it clear how your community is intended to be different from any similar communities.